75 lines
2.8 KiB
Python
75 lines
2.8 KiB
Python
from .error import DecodeError
|
|
|
|
|
|
def bencode(data):
|
|
""" Encoder implementation of the Bencode algorithm (Bittorrent). """
|
|
if isinstance(data, int):
|
|
return b'i%de' % data
|
|
elif isinstance(data, (bytes, bytearray)):
|
|
return b'%d:%s' % (len(data), data)
|
|
elif isinstance(data, str):
|
|
return b'%d:%s' % (len(data), data.encode())
|
|
elif isinstance(data, (list, tuple)):
|
|
encoded_list_items = b''
|
|
for item in data:
|
|
encoded_list_items += bencode(item)
|
|
return b'l%se' % encoded_list_items
|
|
elif isinstance(data, dict):
|
|
encoded_dict_items = b''
|
|
keys = data.keys()
|
|
for key in sorted(keys):
|
|
encoded_dict_items += bencode(key)
|
|
encoded_dict_items += bencode(data[key])
|
|
return b'd%se' % encoded_dict_items
|
|
else:
|
|
raise TypeError("Cannot bencode '%s' object" % type(data))
|
|
|
|
|
|
def bdecode(data):
|
|
""" Decoder implementation of the Bencode algorithm. """
|
|
assert type(data) == bytes # fixme: _maybe_ remove this after porting
|
|
if len(data) == 0:
|
|
raise DecodeError('Cannot decode empty string')
|
|
try:
|
|
return _decode_recursive(data)[0]
|
|
except ValueError as e:
|
|
raise DecodeError(str(e))
|
|
|
|
|
|
def _decode_recursive(data, start_index=0):
|
|
if data[start_index] == ord('i'):
|
|
end_pos = data[start_index:].find(b'e') + start_index
|
|
return int(data[start_index + 1:end_pos]), end_pos + 1
|
|
elif data[start_index] == ord('l'):
|
|
start_index += 1
|
|
decoded_list = []
|
|
while data[start_index] != ord('e'):
|
|
list_data, start_index = _decode_recursive(data, start_index)
|
|
decoded_list.append(list_data)
|
|
return decoded_list, start_index + 1
|
|
elif data[start_index] == ord('d'):
|
|
start_index += 1
|
|
decoded_dict = {}
|
|
while data[start_index] != ord('e'):
|
|
key, start_index = _decode_recursive(data, start_index)
|
|
value, start_index = _decode_recursive(data, start_index)
|
|
decoded_dict[key] = value
|
|
return decoded_dict, start_index
|
|
elif data[start_index] == ord('f'):
|
|
# This (float data type) is a non-standard extension to the original Bencode algorithm
|
|
end_pos = data[start_index:].find(b'e') + start_index
|
|
return float(data[start_index + 1:end_pos]), end_pos + 1
|
|
elif data[start_index] == ord('n'):
|
|
# This (None/NULL data type) is a non-standard extension
|
|
# to the original Bencode algorithm
|
|
return None, start_index + 1
|
|
else:
|
|
split_pos = data[start_index:].find(b':') + start_index
|
|
try:
|
|
length = int(data[start_index:split_pos])
|
|
except ValueError:
|
|
raise DecodeError()
|
|
start_index = split_pos + 1
|
|
end_pos = start_index + length
|
|
b = data[start_index:end_pos]
|
|
return b, end_pos
|